Giant negative magnetoresistance in one-dimensional pi-d system: TPP[Fe(Pc)(CN)(2)](2) (TPP = tetraphenylphosphonium, Pc = phthalocyanine)

We found the giant negative magnetoresistance in the one-dimensional pi-d s ystem TPP[Fe(Pc)(CN)(2)](2) below 50K. The large negative magnetoresistance was observed for the field along the a-axis, while the small one along the c-axis. We also observed the anisotropic Curie behavior of the magnetic su sceptibility. The large (small) magnetoresistance was observed in the field orientation for the large (small) magnetic susceptibility. The reduction o f the spin-flip scattering of the itinerant electrons by the local moments under the magnetic field was proposed as the origin of the negative magneto resistance. In the isostructural compound TPP[Co(Pc)(CN)(2)](2) we observed the large positive magnetoresistance. This positive magnetoresistance cann ot be explained in terms of the orbital effects under the field.